The present invention relates to a powder inhaler and a method of constructing the same.
A number of powder inhalers are known which use different systems for introducing a dose of powder into an air stream. Typically, the powder is inhaled into the lungs of a patient in order to treat, for example, asthma.
One such powder inhaler is disclosed in EP-A-0237507. This inhaler comprises an inhalation channel and a mouthpiece comprising an air chamber and an outlet nozzle, which together define a flow path through which a stream of air is drawn during inhalation by a user. This inhaler further comprises means for introducing powder into the inhalation channel. During inhalation, air is first drawn into and through the inhalation channel so as to pick up powder. The stream of air containing powder is then drawn through the air chamber and out of the outlet nozzle of the mouthpiece.
Powder inhalers are, however, particularly susceptible to the effects of moisture and should therefore include a desiccant, such as silica gel, to absorb any moisture. It will of course be appreciated that it is a requirement that the desiccant be contained entirely separate from the powder to be inhaled so as to avoid contamination of the powder.
In powder inhalers of the kind which comprise an inhaler body and a grip portion at one end thereof, which grip portion is rotatable relative to the inhaler body so as to provide a dose of powder for inhalation, it has been proposed to provide a chamber in the grip portion for containing desiccant. In one proposed construction the grip portion comprises first and second parts which fit together to define a chamber; the first and second parts having cooperating splines to lock the same in the rotational sense and a cooperating circumferential groove and ridge to lock the same axially.
Normally, powder inhalers are assembled automatically by machine. However, automatic assembly would be problematic where the grip portion comprises first and second parts which have to be fitted together. This problem would arise particularly because of the fact that the parts would have to be pressed together with a significant force sufficient at least to engage the ridge and the groove, and, if, as is likely, the parts are not first precisely aligned, both rotationally and axially, the parts could be forced together at an angle such that the splines are damaged and/or the grip portion is not assembled correctly.
It is an aim of the present invention to provide a powder inhaler which includes a chamber for containing desiccant that can be formed simply and reliably.